class OrderReserve(models.Model):
    handbookmodel = models.OneToOneField(HandBookModel, verbose_name=u"Модель")
    reserving = models.ManyToManyField('Reserving', verbose_name=u"Заявки на резеревирование")
    all_quantity_reserve = models.IntegerField(u'Общее количества резерва', null=True, editable=False, default=0)     

    class Meta:
          constraints = (
                                ("check_all_quantity_reserve", Check(all_quantity_reserve__gte = 0)),
                          )

    def save(self):
    	super(OrderReserve, self).save()
	self.all_quantity_reserve = sum(map(lambda x: x.quantity_reserve,self.reserving.all())) 
    	return super(OrderReserve, self).save()    
    
    def was_published_today(self):
        return self.date_pub.date() == datetime.date.today()

    def __unicode__(self):
    	return '%d' % (self.all_quantity_reserve)